[Jeffhs]

In reference to DaveWM's comments regarding radiotron's Toshiba Blackstripe TV with vertical hold issues: You are correct -- cleaning the hold control potentiometer will not in and of itself correct the vertical hold problem. The problem is likely caused by a drifting resistor in the vertical circuits; as the set warms up, the resistor gets closer to its proper value (as the part itself warms up) until it is of the correct value to lock in the vertical. The set will operate normally thereafter, until it is turned off and gets cold; however, when the TV is turned on again and until the resistor warms up, the trouble will return. I'd look for that drifting resistor and replace it, before it gets to the point where it may not return to its rated value even after the set warms up. Problems like this almost always get worse with time, if not corrected.

I don't know for sure, but that set seems like a mid-to-late '80s model, making it close to thirty years old. Any TV that old will have dirty controls (most sets of that vintage still used rotary potentiometers for vertical hold, brightness, contrast, etc.), so a good cleaning can't hurt anything.